Metallocene catalyst system for producing LLDPE copolymers with tear resistance and low haze

ABSTRACT

Ethylene polymers having a density from 0.908 to 0.925 g/cm3, a melt index from 0.5 to 3 g/10 min, a ratio of Mw/Mn from 2 to 4, a ratio of Mz/Mw from 1.6 to 2.3, a CY-a parameter from 0.45 to 0.6, and an ATREF profile characterized by a single peak at a peak ATREF temperature from 76 to 88° C., and by less than 4.5 wt. % of the polymer eluting above a temperature of 91° C. These ethylene polymers can be used to produce various articles of manufacture, such as blown and cast films with a beneficial combination of high tear resistance and low haze.

BACKGROUND OF THE INVENTION

Polyolefins such as high density polyethylene (HDPE) homopolymer andlinear low density polyethylene (LLDPE) copolymer can be produced usingvarious combinations of catalyst systems and polymerization processes.Ziegler-Natta and chromium-based catalyst systems can, for example,produce ethylene polymers having good extrusion processability andpolymer melt strength and bubble stability in blown film applications,typically due to their broad molecular weight distribution (MWD).Metallocene based catalyst systems can, for example, produce ethylenepolymers having excellent impact strength (e.g. dart impact), but oftenat the expense of tear resistance.

In some end-uses, such as blown film and cast film applications, it canbe beneficial to have the impact properties of a metallocene-catalyzedLLDPE copolymer, but with improved tear resistance in combination withgood optical properties. Accordingly, it is to these ends that thepresent invention is generally directed.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify required oressential features of the claimed subject matter. Nor is this summaryintended to be used to limit the scope of the claimed subject matter.

In one aspect, the present invention encompasses ethylene polymers(e.g., ethylene/α-olefin copolymers) characterized by a density in arange from about 0.908 to about 0.925 g/cm³, a melt index in a rangefrom about 0.5 to about 3 g/10 min, a ratio of Mw/Mn in a range fromabout 2 to about 4, a ratio of Mz/Mw in a range from about 1.6 to about2.3, a CY-a parameter in a range from about 0.45 to about 0.6, and anATREF profile characterized by a single peak at a peak ATREF temperaturein a range from about 76 to about 88° C., and by less than or equal toabout 4.5 wt. % of the polymer eluting above a temperature of 91° C.

In another aspect, the present invention encompasses ethylene polymers(e.g., ethylene/α-olefin copolymers) characterized by a density in arange from about 0.908 to about 0.925 g/cm³, a melt index in a rangefrom about 0.5 to about 3 g/10 min, a ratio of Mw/Mn in a range fromabout 2 to about 4, a ratio of Mz/Mw in a range from about 1.6 to about2.3, a CY-a parameter in a range from about 0.45 to about 0.6, an ATREFprofile characterized by a single peak at a peak ATREF temperature in arange from about 76 to about 90° C., by less than or equal to about 12wt. % of the polymer eluting above a temperature of 91° C., and by lessthan or equal to about 0.1 wt. % of the polymer eluting above atemperature of 100° C.

These ethylene polymers can be used to produce various articles ofmanufacture, such as films (e.g., blown films and cast films), sheets,pipes, geomembranes, and molded products. Beneficially, films comprisingor produced from the disclosed ethylene polymers have low haze and hightear resistance, such as haze values of less than 8% and MD tearstrengths over 250 g/mil.

Both the foregoing summary and the following detailed descriptionprovide examples and are explanatory only. Accordingly, the foregoingsummary and the following detailed description should not be consideredto be restrictive. Further, features or variations may be provided inaddition to those set forth herein. For example, certain aspects andembodiments may be directed to various feature combinations andsub-combinations described in the detailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 presents a plot of the ATREF profile of the polymer of Example 1.

FIG. 2 presents a plot of the ATREF profile of the polymer of Example 2.

FIG. 3 presents a plot of the ATREF profile of the polymer of Example 3.

FIG. 4 presents a plot of the ATREF profile of the polymer of Example 4.

FIG. 5 presents a plot of the ATREF profile of the polymer of Example 5.

FIG. 6 presents a plot of the ATREF profile of the polymer of Example 6.

FIG. 7 presents a plot of the ATREF profile of the polymer of Example 7.

FIG. 8 presents a plot of the ATREF profile of the polymer of Example 8.

FIG. 9 presents a plot of the molecular weight distribution of thepolymer of Example 1.

DEFINITIONS

To define more clearly the terms used herein, the following definitionsare provided. Unless otherwise indicated, the following definitions areapplicable to this disclosure. If a term is used in this disclosure butis not specifically defined herein, the definition from the IUPACCompendium of Chemical Terminology, 2nd Ed (1997), can be applied, aslong as that definition does not conflict with any other disclosure ordefinition applied herein, or render indefinite or non-enabled any claimto which that definition is applied. To the extent that any definitionor usage provided by any document incorporated herein by referenceconflicts with the definition or usage provided herein, the definitionor usage provided herein controls.

Herein, features of the subject matter are described such that, withinparticular aspects, a combination of different features can beenvisioned. For each and every aspect and/or feature disclosed herein,all combinations that do not detrimentally affect the designs,compositions, and/or methods described herein are contemplated with orwithout explicit description of the particular combination.Additionally, unless explicitly recited otherwise, any aspect and/orfeature disclosed herein can be combined to describe inventive featuresconsistent with the present disclosure.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodsalso can “consist essentially of” or “consist of” the various componentsor steps, unless stated otherwise. For example, a catalyst compositionconsistent with aspects of the present invention can comprise;alternatively, can consist essentially of; or alternatively, can consistof; an unbridged metallocene compound, an activator, and a co-catalyst.

The terms “a,” “an,” “the,” etc., are intended to include pluralalternatives, e.g., at least one, unless otherwise specified. Forinstance, the disclosure of “an activator-support” or “a metallocenecompound” is meant to encompass one, or mixtures or combinations of morethan one, activator-support or metallocene compound, respectively,unless otherwise specified.

Generally, groups of elements are indicated using the numbering schemeindicated in the version of the periodic table of elements published inChemical and Engineering News, 63(5), 27, 1985. In some instances, agroup of elements can be indicated using a common name assigned to thegroup; for example, alkali metals for Group 1 elements, alkaline earthmetals for Group 2 elements, transition metals for Group 3-12 elements,and halogens or halides for Group 17 elements.

For any particular compound disclosed herein, the general structure orname presented is also intended to encompass all structural isomers,conformational isomers, and stereoisomers that can arise from aparticular set of substituents, unless indicated otherwise. Thus, ageneral reference to a compound includes all structural isomers unlessexplicitly indicated otherwise; e.g., a general reference to pentaneincludes n-pentane, 2-methyl-butane, and 2,2-dimethylpropane, while ageneral reference to a butyl group includes an n-butyl group, asec-butyl group, an iso-butyl group, and a tert-butyl group.Additionally, the reference to a general structure or name encompassesall enantiomers, diastereomers, and other optical isomers whether inenantiomeric or racemic forms, as well as mixtures of stereoisomers, asthe context permits or requires. For any particular formula or name thatis presented, any general formula or name presented also encompasses allconformational isomers, regioisomers, and stereoisomers that can arisefrom a particular set of substituents.

The term “substituted” when used to describe a group, for example, whenreferring to a substituted analog of a particular group, is intended todescribe any non-hydrogen moiety that formally replaces a hydrogen inthat group, and is intended to be non-limiting. A group or groups canalso be referred to herein as “unsubstituted” or by equivalent termssuch as “non-substituted,” which refers to the original group in which anon-hydrogen moiety does not replace a hydrogen within that group.Unless otherwise specified, “substituted” is intended to be non-limitingand include inorganic substituents or organic substituents as understoodby one of ordinary skill in the art.

The term “hydrocarbon” whenever used in this specification and claimsrefers to a compound containing only carbon and hydrogen. Otheridentifiers can be utilized to indicate the presence of particulargroups in the hydrocarbon (e.g., halogenated hydrocarbon indicates thepresence of one or more halogen atoms replacing an equivalent number ofhydrogen atoms in the hydrocarbon). The term “hydrocarbyl group” is usedherein in accordance with the definition specified by IUPAC: a univalentgroup formed by removing a hydrogen atom from a hydrocarbon (that is, agroup containing only carbon and hydrogen). Non-limiting examples ofhydrocarbyl groups include alkyl, alkenyl, aryl, and aralkyl groups,amongst other groups.

The term “polymer” is used herein generically to include olefinhomopolymers, copolymers, terpolymers, and the like, as well as alloysand blends thereof. The term “polymer” also includes impact, block,graft, random, and alternating copolymers. A copolymer is derived froman olefin monomer and one olefin comonomer, while a terpolymer isderived from an olefin monomer and two olefin comonomers. Accordingly,“polymer” encompasses copolymers and terpolymers derived from any olefinmonomer and comonomer(s) disclosed herein. Similarly, the scope of theterm “polymerization” includes homopolymerization, copolymerization, andterpolymerization. Therefore, an ethylene polymer includes ethylenehomopolymers, ethylene copolymers (e.g., ethylene/α-olefin copolymers),ethylene terpolymers, and the like, as well as blends or mixturesthereof. Thus, an ethylene polymer encompasses polymers often referredto in the art as LLDPE (linear low density polyethylene) and HDPE (highdensity polyethylene). As an example, an olefin copolymer, such as anethylene copolymer, can be derived from ethylene and a comonomer, suchas 1-butene, 1-hexene, or 1-octene. If the monomer and comonomer wereethylene and 1-hexene, respectively, the resulting polymer can becategorized an as ethylene/1-hexene copolymer. The term “polymer” alsoincludes all possible geometrical configurations, unless statedotherwise, and such configurations can include isotactic, syndiotactic,and random symmetries. Moreover, unless stated otherwise, the term“polymer” also is meant to include all molecular weight polymers, and isinclusive of lower molecular weight polymers.

The term “co-catalyst” is used generally herein to refer to compoundssuch as aluminoxane compounds, organoboron or organoborate compounds,ionizing ionic compounds, organoaluminum compounds, organozinccompounds, organomagnesium compounds, organolithium compounds, and thelike, that can constitute one component of a catalyst composition, whenused, for example, in addition to an activator-support. The term“co-catalyst” is used regardless of the actual function of the compoundor any chemical mechanism by which the compound may operate.

The terms “chemically-treated solid oxide,” “treated solid oxidecompound,” and the like, are used herein to indicate a solid, inorganicoxide of relatively high porosity, which can exhibit Lewis acidic orBrønsted acidic behavior, and which has been treated with anelectron-withdrawing component, typically an anion, and which iscalcined. The electron-withdrawing component is typically anelectron-withdrawing anion source compound. Thus, the chemically-treatedsolid oxide can comprise a calcined contact product of at least onesolid oxide with at least one electron-withdrawing anion sourcecompound. Typically, the chemically-treated solid oxide comprises atleast one acidic solid oxide compound. The “activator-support” of thepresent invention can be a chemically-treated solid oxide. The terms“support” and “activator-support” are not used to imply these componentsare inert, and such components should not be construed as an inertcomponent of the catalyst composition. The term “activator,” as usedherein, refers generally to a substance that is capable of converting ametallocene component into a catalyst that can polymerize olefins, orconverting a contact product of a metallocene component and a componentthat provides an activatable ligand (e.g., an alkyl, a hydride) to themetallocene, when the metallocene compound does not already comprisesuch a ligand, into a catalyst that can polymerize olefins. This term isused regardless of the actual activating mechanism. Illustrativeactivators include activator-supports, aluminoxanes, organoboron ororganoborate compounds, ionizing ionic compounds, and the like.Aluminoxanes, organoboron or organoborate compounds, and ionizing ioniccompounds generally are referred to as activators if used in a catalystcomposition in which an activator-support is not present. If thecatalyst composition contains an activator-support, then thealuminoxane, organoboron or organoborate, and ionizing ionic materialsare typically referred to as co-catalysts.

The term “metallocene” as used herein describes compounds comprising atleast one η³ to η⁵-cycloalkadienyl-type moiety, wherein η³ toη⁵-cycloalkadienyl moieties include cyclopentadienyl ligands, indenylligands, fluorenyl ligands, and the like, including partially saturatedor substituted derivatives or analogs of any of these. Possiblesubstituents on these ligands can include H, therefore this inventioncomprises ligands such as tetrahydroindenyl, tetrahydrofluorenyl,octahydrofluorenyl, partially saturated indenyl, partially saturatedfluorenyl, substituted partially saturated indenyl, substitutedpartially saturated fluorenyl, and the like. In some contexts, themetallocene is referred to simply as the “catalyst,” in much the sameway the term “co-catalyst” is used herein to refer to, for example, anorganoaluminum compound.

The terms “catalyst composition,” “catalyst mixture,” “catalyst system,”and the like, do not depend upon the actual product or compositionresulting from the contact or reaction of the initial components of thedisclosed or claimed catalyst composition/mixture/system, the nature ofthe active catalytic site, or the fate of the co-catalyst, the unbridgedmetallocene compound, or the activator (e.g., activator-support), aftercombining these components. Therefore, the terms “catalyst composition,”“catalyst mixture,” “catalyst system,” and the like, encompass theinitial starting components of the composition, as well as whateverproduct(s) may result from contacting these initial starting components,and this is inclusive of both heterogeneous and homogenous catalystsystems or compositions. The terms “catalyst composition,” “catalystmixture,” “catalyst system,” and the like, can be used interchangeablythroughout this disclosure.

The term “contact product” is used herein to describe compositionswherein the components are contacted together in any order, in anymanner, and for any length of time, unless otherwise specified. Forexample, the components can be contacted by blending or mixing. Further,contacting of any component can occur in the presence or absence of anyother component of the compositions described herein. Combiningadditional materials or components can be done by any suitable method.Further, the term “contact product” includes mixtures, blends,solutions, slurries, reaction products, and the like, or combinationsthereof. Although “contact product” can include reaction products, it isnot required for the respective components to react with one another.Similarly, the term “contacting” is used herein to refer to materialswhich can be blended, mixed, slurried, dissolved, reacted, treated, orotherwise combined in some other manner.

Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of theinvention, the typical methods, devices, and materials are hereindescribed.

All publications and patents mentioned herein are incorporated herein byreference for the purpose of describing and disclosing, for example, theconstructs and methodologies that are described in the publications,which might be used in connection with the presently describedinvention.

Several types of ranges are disclosed in the present invention. When arange of any type is disclosed or claimed, the intent is to disclose orclaim individually each possible number that such a range couldreasonably encompass, including end points of the range as well as anysub-ranges and combinations of sub-ranges encompassed therein. Forexample, when a chemical moiety having a certain number of carbon atomsis disclosed or claimed, the intent is to disclose or claim individuallyevery possible number that such a range could encompass, consistent withthe disclosure herein. For example, the disclosure that a moiety is a C₁to C₁₈ hydrocarbyl group, or in alternative language, a hydrocarbylgroup having from 1 to 18 carbon atoms, as used herein, refers to amoiety that can have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,16, 17, or 18 carbon atoms, as well as any range between these twonumbers (for example, a C₁ to C₈ hydrocarbyl group), and also includingany combination of ranges between these two numbers (for example, a C₂to C₄ and a C₁₂ to C₁₆ hydrocarbyl group).

Similarly, another representative example follows for the ratio of Mw/Mnof an ethylene polymer consistent with aspects of this invention. By adisclosure that the ratio of Mw/Mn can be in a range from about 2 toabout 4, the intent is to recite that the ratio of Mw/Mn can be anyratio in the range and, for example, can be equal to about 2, about 2.2,about 2.4, about 2.6, about 2.8, about 3, about 3.2, about 3.4, about3.6, about 3.8, or about 4. Additionally, the ratio of Mw/Mn can bewithin any range from about 2 to about 4 (for example, from about 2.3 toabout 3.6), and this also includes any combination of ranges betweenabout 2 and about 4 (for example, the Mw/Mn ratio can be in a range fromabout 2 to about 2.7, or from about 3.3 to about 3.8). Further, in allinstances, where “about” a particular value is disclosed, then thatvalue itself is disclosed. Thus, the disclosure that the ratio of Mw/Mncan be from about 2 to about 4 also discloses a ratio of Mw/Mn from 2 to4 (for example, from 2.3 to 3.6), and this also includes any combinationof ranges between 2 and 4 (for example, the Mw/Mn ratio can be in arange from 2 to 2.7, or from 3.3 to 3.8). Likewise, all other rangesdisclosed herein should be interpreted in a manner similar to theseexamples.

The term “about” means that amounts, sizes, formulations, parameters,and other quantities and characteristics are not and need not be exact,but can be approximate and/or larger or smaller, as desired, reflectingtolerances, conversion factors, rounding off, measurement errors, andthe like, and other factors known to those of skill in the art. Ingeneral, an amount, size, formulation, parameter or other quantity orcharacteristic is “about” or “approximate” whether or not expresslystated to be such. The term “about” also encompasses amounts that differdue to different equilibrium conditions for a composition resulting froma particular initial mixture. Whether or not modified by the term“about,” the claims include equivalents to the quantities. The term“about” can mean within 10% of the reported numerical value, preferablywithin 5% of the reported numerical value.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed generally to ethylene-based polymershaving excellent impact and toughness properties, but with improved tearresistance and optical properties. Articles produced from theseethylene-based polymers, such as blown and cast films, can have anunexpected combination of both high tear strength and low haze.

Ethylene Polymers

Generally, the polymers disclosed herein are ethylene-based polymers, orethylene polymers, encompassing homopolymers of ethylene as well ascopolymers, terpolymers, etc., of ethylene and at least one olefincomonomer. Comonomers that can be copolymerized with ethylene often canhave from 3 to 20 carbon atoms in their molecular chain. For example,typical comonomers can include, but are not limited to, propylene,1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and the like, orcombinations thereof. In an aspect, the olefin comonomer can comprise aC₃-C₁₈ olefin; alternatively, the olefin comonomer can comprise a C₃-C₁₀olefin; alternatively, the olefin comonomer can comprise a C₄-C₁₀olefin; alternatively, the olefin comonomer can comprise a C₃-C₁₀α-olefin; alternatively, the olefin comonomer can comprise a C₄-C₁₀α-olefin; alternatively, the olefin comonomer can comprise 1-butene,1-hexene, 1-octene, or any combination thereof or alternatively, thecomonomer can comprise 1-hexene. Typically, the amount of the comonomer,based on the total weight of monomer (ethylene) and comonomer, can be ina range from about 0.01 to about 20 wt. %, from about 0.1 to about 10wt. %, from about 0.5 to about 15 wt. %, from about 0.5 to about 8 wt.%, or from about 1 to about 15 wt. %.

In one aspect, the ethylene polymer of this invention can comprise anethylene/α-olefin copolymer, while in another aspect, the ethylenepolymer can comprise an ethylene homopolymer, and in yet another aspect,the ethylene polymer of this invention can comprise an ethylene/α-olefincopolymer and an ethylene homopolymer. For example, the ethylene polymercan comprise an ethylene/1-butene copolymer, an ethylene/1-hexenecopolymer, an ethylene/1-octene copolymer, or any combination thereof;alternatively, an ethylene/1-butene copolymer; alternatively, anethylene/1-hexene copolymer; or alternatively, an ethylene/1-octenecopolymer.

An illustrative and non-limiting example of an ethylene polymer (e.g.,an ethylene copolymer) of the present invention can have a density in arange from about 0.908 to about 0.925 g/cm³, a melt index in a rangefrom about 0.5 to about 3 g/10 min, a ratio of Mw/Mn in a range fromabout 2 to about 4, a ratio of Mz/Mw in a range from about 1.6 to about2.3, a CY-a parameter in a range from about 0.45 to about 0.6, and anATREF profile characterized by a single peak at a peak ATREF temperature(temperature of the highest peak on the ATREF curve) in a range fromabout 76 to about 88° C., and by less than or equal to about 4.5 wt. %of the polymer eluting above a temperature of 91° C. In some aspects,less than or equal to about 4 wt. %, or less than or equal to about 3.5wt. %, or less than or equal to about 3 wt. %, of the polymer elutesabove a temperature of 91° C.

Another illustrative and non-limiting example of an ethylene polymer ofthe present invention can have a density in a range from about 0.908 toabout 0.925 g/cm³, a melt index in a range from about 0.5 to about 3g/10 min, a ratio of Mw/Mn in a range from about 2 to about 4, a ratioof Mz/Mw in a range from about 1.6 to about 2.3, a CY-a parameter in arange from about 0.45 to about 0.6, an ATREF profile characterized by asingle peak at a peak ATREF temperature in a range from about 76 toabout 90° C., by less than or equal to about 12 wt. % of the polymereluting above a temperature of 91° C., and by less than or equal toabout 0.1 wt. % of the polymer eluting above a temperature of 100° C. Insome aspects, less than or equal to about 11 wt. %, or less than orequal to about 10 wt. %, or less than or equal to about 4.5 wt. %, orless than or equal to about 3.5 wt. %, of the polymer elutes above atemperature of 91° C.

These illustrative and non-limiting examples of ethylene polymersconsistent with the present invention also can have any of the polymerproperties listed below and in any combination, unless indicatedotherwise.

The densities of ethylene-based polymers disclosed herein often are lessthan or equal to about 0.925 g/cm³, for example, less than or equal toabout 0.922 g/cm³. Yet, in particular aspects, the density can be in arange from about 0.908 to about 0.925 g/cm³, from about 0.908 to about0.922 g/cm³, from about 0.908 to about 0.92 g/cm³, from about 0.91 toabout 0.925 g/cm³, from about 0.91 to about 0.922 g/cm³, or from about0.91 to about 0.92 g/cm³.

While not being limited thereto, ethylene polymers described hereinoften can have a melt index (MI) in a range from about 0.5 to about 3g/10 min, from about 0.5 to about 2.5 g/10 min, or from about 0.5 toabout 2.2 g/10 min. In further aspects, ethylene polymers describedherein can have a melt index (MI) in a range from about 0.8 to about 2.5g/10 min, from about 0.8 to about 2.2 g/10 min, from about 1 to about2.5 g/10 min, from about 1 to about 2.2 g/10 min, or from about 1.6 toabout 2.4 g/10 min.

Typically, the ethylene polymer can have a high load melt index (HLMI)in a range from about 10 to about 50 g/10 min; alternatively, from about12 to about 45 g/10 min; alternatively, from about 12 to about 40 g/10min; alternatively, from about 18 to about 45 g/10 min; alternatively,from about 15 to about 40 g/10 min; or alternatively, from about 25 toabout 40 g/10 min.

The ratio of HLMI/MI of the ethylene polymer can fall in a range fromabout 10 to about 30, from about 10 to about 25, or from about 10 toabout 20 in some aspects, while in other aspects, the ratio of HLMI/MIranges from about 15 to about 30, from about 15 to about 25, from about15 to about 22, or from about 15 to about 20.

In an aspect, ethylene polymers described herein can have a ratio ofMw/Mn, or the polydispersity index, in a range from about 2 to about 4,from about 2 to about 3.8, from about 2 to about 3.6, or from about 2 toabout 3.5. In another aspect, ethylene polymers described herein canhave a Mw/Mn in a range from about 2.2 to about 4, from about 2.2 toabout 3.8, from about 2.2 to about 3.7, from about 2.3 to about 3.6,from about 2.3 to about 3.6, from about 2.4 to about 4, from about 2.4to about 3.8, or from about 2.4 to about 3.7. Additionally oralternatively, the ethylene polymers can have a ratio of Mz/Mw in arange from about 1.6 to about 2.3, from about 1.7 to about 2.3, or fromabout 1.8 to about 2.3. In another aspect, ethylene polymers describedherein can have a Mz/Mw in a range from about 1.6 to about 2.2, fromabout 1.7 to about 2.2, from about 1.8 to about 2.2, from about 1.7 toabout 2.1, from about 1.8 to about 2.1, or from about 1.8 to about 2.

In an aspect, ethylene polymers described herein can have aweight-average molecular weight (Mw) in a range from about 80,000 toabout 180,000 g/mol, from about 80,000 to about 160,000 g/mol, or fromabout 80,000 to about 120,000 g/mol. In another aspect, ethylenepolymers described herein can have a Mw in a range from about 95,000 toabout 175,000 g/mol, from about 95,000 to about 140,000 g/mol, fromabout 95,000 to about 115,000 g/mol, or from about 100,000 to about110,000 g/mol. Additionally or alternatively, the ethylene polymers canhave a number-average molecular weight (Mn) in a range from about 20,000to about 60,000 g/mol, from about 20,000 to about 55,000 g/mol, or fromabout 20,000 to about 50,000 g/mol. In another aspect, the ethylenepolymers can have a Mn in a range from about 25,000 to about 60,000g/mol, from about 25,000 to about 55,000 g/mol, from about 25,000 toabout 50,000 g/mol, or from about 25,000 to about 45,000 g/mol.Additionally or alternatively, the ethylene polymers can have az-average molecular weight (Mz) in a range from about 150,000 to about400,000, from about 150,000 to about 300,000 g/mol, or from about175,000 to about 325,000 g/mol. In another aspect, the ethylene polymerscan have a Mz in a range from about 175,000 to about 275,000 g/mol, fromabout 175,000 to about 250,000 g/mol, from about 175,000 to about225,000, from about 185,000 to about 265,000 g/mol, or from about185,000 to about 235,000 g/mol. Additionally or alternatively, theethylene polymers can have a peak molecular weight (Mp) in a range fromabout 50,000 to about 200,000 g/mol, from about 60,000 to about 130,000g/mol, from about 60,000 to about 115,000 g/mol, or from about 65,000 toabout 120,000 g/mol. In another aspect, the ethylene polymers can have aMp in a range from about 70,000 to about 130,000 g/mol, from about70,000 to about 115,000 g/mol, or from about 75,000 to about 95,000g/mol.

In accordance with certain aspects of this invention, the IB parameterfrom a molecular weight distribution curve (plot of dW/d(Log M) vs. LogM; normalized to an area equal to 1) can be an important characteristicof the ethylene polymers described herein. The IB parameter is oftenreferred to as the integral breadth, and is defined as 1/[dW/d(LogM)]_(MAX), and is useful to describe a polymer having a relativelynarrow molecular weight distribution with a small fraction of both highmolecular weight and low molecular weight tails. Generally, the IBparameter of the ethylene polymers consistent with this invention can bein a range from about 0.9 to about 1.05, from about 0.92 to about 1.05,or from about 0.93 to about 1.05. In one aspect, the ethylene polymercan be characterized by an IB parameter in a range from about 0.91 toabout 1.03, and in another aspect, from about 0.93 to about 1.03, and inyet another aspect, from about 0.95 to about 1.03.

Generally, ethylene polymers consistent with certain aspects of theinvention can have a unimodal molecular weight distribution (asdetermined using gel permeation chromatography (GPC) or other relatedanalytical technique). In a unimodal molecular weight distribution,there is a single identifiable peak.

While not limited thereto, ethylene polymers described herein can have aCY-a parameter of from about 0.45 to about 0.6, from about 0.45 to about0.58, from about 0.48 to about 0.6, or from about 0.48 to about 0.58 insome aspects, while in other aspects, the CY-a parameter can range fromabout 0.5 to about 0.6, from about 0.52 to about 0.59, or from about0.52 to about 0.58, and the like. Additionally or alternatively, theseethylene polymers can be characterized by a τ_(η) (relaxation time insec) that often can range from about 4×10⁻³ sec to about 2×10⁻² sec;alternatively, from about 5×10⁻³ sec to about 1×10⁻² sec; oralternatively, from about 5×10⁻³ sec to about 9×10⁻³ sec. Theserheological parameters are determined from viscosity data measured at190° C. and using the Carreau-Yasuda (CY) empirical model as describedherein.

In accordance with certain aspects of this invention, the ethylenepolymers described herein can have a unique ATREF profile. For instance,the ethylene polymer can have a peak ATREF temperature (temperature ofthe highest peak on the ATREF curve in the 40-110° C. range) of fromabout 76 to about 90° C., or from about 76 to about 88° C. In someaspects, the peak ATREF temperature can be in a range from about 77 toabout 89° C., from about 76 to about 87° C., from about 78 to about 87°C., or from about 79 to about 86° C. Moreover, only a small fraction ofthe disclosed ethylene polymers elutes above a temperature of 91° C.:less than or equal to about 12 wt. %, less than or equal to about 11 wt.%, or less than or equal to about 10 wt. % in one aspect, and less thanor equal to about 4.5 wt. %, less than or equal to about 4 wt. %, lessthan or equal to about 3.5 wt. %, or less than or equal to about 3 wt. %in another aspect. Further, an even smaller fraction of the disclosedethylene polymers elutes above a temperature of 100° C.: less than orequal to about 0.1 wt. %, less than or equal to about 0.09 wt. %, lessthan or equal to about 0.07 wt. %, or less than or equal to about 0.05wt. %, and the like.

Additionally or alternatively, the ethylene polymer (e.g., theethylene/α-olefin copolymer) can have an ATREF profile characterized byfrom about 0.05 to about 5 wt. % (or from about 0.1 to about 3 wt. %, orfrom about 0.3 to about 2 wt. %) of the polymer eluting below atemperature of 40° C.; by from about 14 to about 45 wt. % (or from about16 to about 44 wt. %, or from about 22 to about 42 wt. %) of the polymereluting between 40 and 76° C.; by from about 35 to about 53 wt. % (orfrom about 38 to about 52 wt. %, or from about 40 to about 51 wt. %) ofthe polymer eluting between 76 and 86° C.; and the remainder of thepolymer (to reach 100 wt. %) eluting above a temperature of 86° C.

In an aspect, the ethylene polymer described herein can be a reactorproduct (e.g., a single reactor product), for example, not apost-reactor blend of two polymers, for instance, having differentmolecular weight characteristics. As one of skill in the art wouldreadily recognize, physical blends of two different polymer resins canbe made, but this necessitates additional processing and complexity notrequired for a reactor product. Additionally, the ethylene polymer canfurther contain any suitable additive, non-limiting examples of whichinclude an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a filler, a polymer processing aid, a UV additive,and the like, as well as any combination thereof.

Moreover, the ethylene polymers can be produced with a metallocenecatalyst system containing zirconium, discussed further below.Ziegler-Natta and hafnium metallocene based catalysts systems are notrequired. Therefore, the ethylene polymer can contain no measurableamount of titanium or hafnium (catalyst residue), i.e., less than 0.1ppm by weight. In some aspects, the ethylene polymer can contain,independently, less than 0.08 ppm, less than 0.05 ppm, or less than 0.03ppm, of titanium and hafnium.

Articles and Products

Articles of manufacture can be formed from, and/or can comprise, theethylene polymers of this invention and, accordingly, are encompassedherein. For example, articles which can comprise ethylene polymers ofthis invention can include, but are not limited to, an agriculturalfilm, an automobile part, a bottle, a container for chemicals, a drum, afiber or fabric, a food packaging film or container, a food servicearticle, a fuel tank, a geomembrane, a household container, a liner, amolded product, a medical device or material, an outdoor storageproduct, outdoor play equipment, a pipe, a sheet or tape, a toy, or atraffic barrier, and the like. Various processes can be employed to formthese articles. Non-limiting examples of these processes includeinjection molding, blow molding, rotational molding, film extrusion,sheet extrusion, profile extrusion, thermoforming, and the like.Additionally, additives and modifiers are often added to these polymersin order to provide beneficial polymer processing or end-use productattributes. Such processes and materials are described in ModernPlastics Encyclopedia, Mid-November 1995 Issue, Vol. 72, No. 12; andFilm Extrusion Manual—Process, Materials, Properties, TAPPI Press, 1992;the disclosures of which are incorporated herein by reference in theirentirety. In some aspects of this invention, an article of manufacturecan comprise any of ethylene polymers described herein, and the articleof manufacture can be or can comprise a blown film or a cast film.

In some aspects, the article produced from and/or comprising an ethylenepolymer of this invention is a film product. For instance, the film canbe a blown film or a cast film that is produced from and/or comprisesany of the ethylene polymers disclosed herein. Such films also cancontain one or more additives, non-limiting examples of which caninclude an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a filler, a processing aid, a UV inhibitor, andthe like, as well as combinations thereof.

Also contemplated herein is a method for forming or preparing an articleof manufacture comprising any ethylene polymer disclosed herein. Forinstance, a method can comprise (i) contacting a catalyst compositionwith ethylene and an olefin comonomer under polymerization conditions ina polymerization reactor system to produce an ethylene polymer, whereinthe catalyst composition can comprise an unbridged metallocene compound,an activator (e.g., an activator-support comprising a solid oxidetreated with an electron-withdrawing anion), and co-catalyst (e.g., anorganoaluminum compound); and (ii) forming an article of manufacturecomprising the ethylene polymer. The forming step can comprise blending,melt processing, extruding, molding, or thermoforming, and the like,including combinations thereof.

Also contemplated herein is a method for making a film (e.g., a blownfilm or a cast film) comprising any ethylene polymer disclosed herein.For instance, the method can comprise melt processing the ethylenepolymer through a die to form the film. Suitably, the die can beconfigured based on the film to be produced, for example, an annularblown film die to produce a blown film, a slot or cast film die toproduce a cast film, and so forth. Moreover, any suitable means of meltprocessing can be employed, although extrusion typically can beutilized. As above, additives can be combined with the polymer in themelt processing step (extrusion step), such as antioxidants, acidscavengers, antiblock additives, slip additives, colorants, fillers,processing aids, UV inhibitors, and the like, as well as combinationsthereof.

Films disclosed herein, whether cast or blown, can be any thickness thatis suitable for the particular end-use application, and often, theaverage film thickness can be in a range from about 0.25 to about 250mils, or from about 0.5 to about 20 mils. For certain film applications,typical average thicknesses can be in a range from about 0.25 to about 8mils, from about 0.5 to about 8 mils, from about 0.8 to about 5 mils, orfrom about 0.7 to about 2 mils.

In an aspect and unexpectedly, the blown films or cast films disclosedherein can have excellent tear resistance. Further, such films also canhave very low haze, as compared to conventional blown films of generallythe same nominal density. For instance, the tear resistance of the filmsdescribed herein can be characterized by the MD (or TD) Elmendorf tearstrength. Suitable ranges for the MD tear strength can include, but arenot limited to, from about 200 to about 500 g/mil, from about 250 toabout 500 g/mil, from about 300 to about 500 g/mil, from about 250 toabout 400 g/mil, from about 300 to about 400 g/mil, or from about 275 toabout 350 g/mil, and the like. Typical ranges for the TD tear strengthcan include, but are not limited to, from about 300 to about 800 g/mil,from about 300 to about 700 g/mil, from about 300 to about 625 g/mil, orfrom about 350 to about 650 g/mil, and the like.

While not being limited thereto, the blown film or cast film can have aratio of MD Elmendorf tear strength to TD Elmendorf tear strength(MD:TD) in a range from about 0.3:1 to about 0.9:1, such as from about0.4:1 to about 0.9:1, from about 0.5:1 to about 0.9:1, from about 0.45:1to about 0.9:1, or from about 0.5:1 to about 0.85:1.

In some aspects, the film can have a dart impact greater than or equalto about 300 g/mil, greater than or equal to about 500 g/mil, greaterthan or equal to about 750 g/mil, greater than or equal to about 1000g/mil, greater than or equal to about 1200 g/mil, or greater than orequal to about 1400 g/mil, and often can range up to about 1500-2000g/mil or more. For many film applications, the upper limit on dartimpact is not determined, so long as the dart impact exceeds aparticular minimal value or threshold.

The film products encompassed herein also can be characterized by verygood optical properties, such as low haze. As one of skill in the artwould readily recognize, certain additives can adversely impact haze andother optical properties, for example, slip and antiblock additives.Nonetheless, the film products encompassed herein can have a haze (withor without additives) of less than or equal to about 10%, or less thanor equal to about 8%, and often can have haze values ranging from about2 to about 10%, from about 2 to about 8%, from about 2 to about 7%, orfrom about 2 to about 6%, and the like. Additionally or alternatively,the blown film or cast film can have a clarity (with or withoutadditives) of at least about 70% in one aspect, at least about 75% inanother aspect, and at least about 80% in yet another aspect.

Catalyst Systems and Polymerization Processes

In accordance with aspects of the present invention, the olefin polymer(e.g., the ethylene copolymer) can be produced using a metallocene-basedcatalyst system. In these aspects, the metallocene catalyst can compriseany suitable unbridged metallocene compound, or any unbridgedmetallocene compound disclosed herein. The catalyst system also cancomprise any suitable activator or any activator disclosed herein, andoptionally, any suitable co-catalyst or any co-catalyst disclosedherein.

Referring first to the metallocene component, the unbridged metallocenecompound can comprise an unbridged zirconium or hafnium basedmetallocene compound containing two cyclopentadienyl groups, two indenylgroups, or a cyclopentadienyl and an indenyl group. In another aspect,the unbridged metallocene compound can comprise an unbridged zirconiumbased metallocene compound containing two cyclopentadienyl groups. Inyet another aspect, the unbridged metallocene compound can comprise anunbridged zirconium based metallocene compound containing two indenylgroups.

Further, the cyclopentadienyl and/or indenyl groups can be substitutedor unsubstituted. As an example, one (or both) of the cyclopentadienyland/or indenyl groups of the unbridged metallocene compound can have ahydrocarbyl group as a substituent. Generally, the hydrocarbyl groupwhich can be a substituent on a cyclopentadienyl group (or an indenylgroup) can be a C₁ to C₃₆ hydrocarbyl group, including a C₁ to C₃₆ alkylgroup, a C₂ to C₃₆ alkenyl group, a C₄ to C₃₆ cycloalkyl group, a C₆ toC₃₆ aryl group, or a C₇ to C₃₆ aralkyl group. For instance, eachsubstituent independently can be a C₁ to C₁₈ alkyl group, a C₂ to C₁₈alkenyl group, a C₄ to C₁₈ cycloalkyl group, a C₆ to C₁₈ aryl group, ora C₇ to C₁₈ aralkyl group; alternatively, a C₁ to C₁₂ alkyl group, a C₂to C₁₂ alkenyl group, a C₄ to C₁₂ cycloalkyl group, a C₆ to C₁₂ arylgroup, or a C₇ to C₁₂ aralkyl group; alternatively, a C₁ to C₁₀ alkylgroup, a C₂ to C₁₀ alkenyl group, a C₄ to C₁₀ cycloalkyl group, a C₆ toC₁₀ aryl group, or a C₇ to C₁₀ aralkyl group; or alternatively, a C₁ toC₅ alkyl group, a C₂ to C₅ alkenyl group, a C₅ to C₈ cycloalkyl group, aC₆ to C₈ aryl group, or a C₇ to C₈ aralkyl group.

Suitable alkyl groups that can be substituents on the cyclopentadienylgroup (or the indenyl group) can include a methyl group, an ethyl group,a propyl group, a butyl group (e.g., t-Bu or n-Bu), a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group, or a decylgroup, and the like.

Illustrative and non-limiting examples of unbridged metallocenecompounds suitable for use in the metallocene-based catalyst system caninclude the following compounds (Ph=phenyl):

and the like, as well as combinations thereof.

The catalyst system is not limited solely to unbridged metallocenecompounds such as described above. Other suitable unbridged metallocenecompounds are disclosed in U.S. Pat. Nos. 7,199,073, 7,226,886,7,312,283, and 7,619,047, which are incorporated herein by reference intheir entirety.

Additionally, the catalyst system contains an activator. For example,the catalyst system can contain an activator-support, an aluminoxanecompound, an organoboron or organoborate compound, an ionizing ioniccompound, and the like, or any combination thereof. The catalyst systemcan contain one or more than one activator.

In one aspect, the catalyst system can comprise an aluminoxane compound,an organoboron or organoborate compound, an ionizing ionic compound, andthe like, or a combination thereof. Examples of such activators aredisclosed in, for instance, U.S. Pat. Nos. 3,242,099, 4,794,096,4,808,561, 5,576,259, 5,807,938, 5,919,983, and 8,114,946, thedisclosures of which are incorporated herein by reference in theirentirety. In another aspect, the catalyst system can comprise analuminoxane compound. In yet another aspect, the catalyst system cancomprise an organoboron or organoborate compound. In still anotheraspect, the catalyst system can comprise an ionizing ionic compound.

In other aspects, the catalyst system can comprise an activator-support,for example, an activator-support comprising a solid oxide treated withan electron-withdrawing anion. Examples of such materials are disclosedin, for instance, U.S. Pat. Nos. 7,294,599, 7,601,665, 7,884,163,8,309,485, 8,623,973, and 9,023,959, which are incorporated herein byreference in their entirety. Thus, the activator-support can comprisefluorided alumina, chlorided alumina, bromided alumina, sulfatedalumina, fluorided silica-alumina, chlorided silica-alumina, bromidedsilica-alumina, sulfated silica-alumina, fluorided silica-zirconia,chlorided silica-zirconia, bromided silica-zirconia, sulfatedsilica-zirconia, fluorided silica-titania, fluorided-chloridedsilica-coated alumina, fluorided silica-coated alumina, sulfatedsilica-coated alumina, or phosphated silica-coated alumina, and thelike, as well as any combination thereof. In some aspects, theactivator-support can comprise a fluorided solid oxide and/or a sulfatedsolid oxide.

Various processes can be used to form activator-supports useful in thepresent invention. Methods of contacting the solid oxide with theelectron-withdrawing component, suitable electron withdrawing componentsand addition amounts, impregnation with metals or metal ions (e.g.,zinc, nickel, vanadium, titanium, silver, copper, gallium, tin,tungsten, molybdenum, zirconium, and the like, or combinations thereof),and various calcining procedures and conditions are disclosed in, forexample, U.S. Pat. Nos. 6,107,230, 6,165,929, 6,294,494, 6,300,271,6,316,553, 6,355,594, 6,376,415, 6,388,017, 6,391,816, 6,395,666,6,524,987, 6,548,441, 6,548,442, 6,576,583, 6,613,712, 6,632,894,6,667,274, 6,750,302, 7,294,599, 7,601,665, 7,884,163, and 8,309,485,which are incorporated herein by reference in their entirety. Othersuitable processes and procedures for preparing activator-supports(e.g., fluorided or sulfated solid oxides) are well known to those ofskill in the art.

The present invention can employ catalyst compositions containing anunbridged metallocene compound, an activator (one or more than one), andoptionally, a co-catalyst. When present, the co-catalyst can include,but is not limited to, metal alkyl, or organometal, co-catalysts, withthe metal encompassing boron, aluminum, zinc, and the like. Optionally,the catalyst systems provided herein can comprise a co-catalyst, or acombination of co-catalysts. For instance, alkyl boron, alkyl aluminum,and alkyl zinc compounds often can be used as co-catalysts in suchcatalyst systems. Representative boron compounds can include, but arenot limited to, tri-n-butyl borane, tripropylborane, triethylborane, andthe like, and this include combinations of two or more of thesematerials. While not being limited thereto, representative aluminumcompounds (e.g., organoaluminum compounds) can includetrimethylaluminum, triethylaluminum, tri-n-propylaluminum,tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum,tri-n-octylaluminum, diisobutylaluminum hydride, diethylaluminumethoxide, diethylaluminum chloride, and the like, as well as anycombination thereof. Exemplary zinc compounds (e.g., organozinccompounds) that can be used as co-catalysts can include, but are notlimited to, dimethylzinc, diethylzinc, dipropylzinc, dibutylzinc,dineopentylzinc, di(trimethylsilyl)zinc, di(triethylsilyl)zinc,di(triisoproplysilyl)zinc, di(triphenylsilyl)zinc,di(allyldimethylsilyl)zinc, di(trimethylsilylmethyl)zinc, and the like,or combinations thereof. Accordingly, in an aspect of this invention,the catalyst composition can comprise an unbridged metallocene compound,an activator-support, and an organoaluminum compound.

In another aspect of the present invention, a catalyst composition isprovided which comprises an unbridged metallocene compound, anactivator-support, and an organoaluminum compound, wherein this catalystcomposition is substantially free of aluminoxanes, organoboron ororganoborate compounds, ionizing ionic compounds, and/or other similarmaterials; alternatively, substantially free of aluminoxanes;alternatively, substantially free or organoboron or organoboratecompounds; or alternatively, substantially free of ionizing ioniccompounds. In these aspects, the catalyst composition has catalystactivity, discussed herein, in the absence of these additionalmaterials. For example, a catalyst composition of the present inventioncan consist essentially of an unbridged metallocene compound, anactivator-support, and an organoaluminum compound, wherein no othermaterials are present in the catalyst composition which wouldincrease/decrease the activity of the catalyst composition by more thanabout 10% from the catalyst activity of the catalyst composition in theabsence of said materials.

Catalyst compositions of the present invention generally have a catalystactivity greater than about 250 grams of ethylene polymer (homopolymerand/or copolymer, as the context requires) per gram of activator-supportper hour (abbreviated g/g/hr). In another aspect, the catalyst activitycan be greater than about 350, greater than about 450, or greater thanabout 550 g/g/hr. Yet, in another aspect, the catalyst activity can begreater than about 700 g/g/hr, greater than about 1000 g/g/hr, orgreater than about 2000 g/g/hr, and often as high as 5000-10,000 g/g/hr.Illustrative and non-limiting ranges for the catalyst activity includefrom about 500 to about 5000, from about 750 to about 4000, or fromabout 1000 to about 3500 g/g/hr, and the like. These activities aremeasured under slurry polymerization conditions, with atriisobutylaluminum co-catalyst, using isobutane as the diluent, at apolymerization temperature of about 95° C. and a reactor pressure ofabout 590 psig. Moreover, in some aspects, the activator-support cancomprise sulfated alumina, fluorided silica-alumina, or fluoridedsilica-coated alumina, although not limited thereto.

This invention further encompasses methods of making these catalystcompositions, such as, for example, contacting the respective catalystcomponents in any order or sequence. In one aspect, for example, thecatalyst composition can be produced by a process comprising contacting,in any order, the unbridged metallocene compound, the activator, and theco-catalyst.

Olefin polymers (e.g., ethylene polymers) can be produced from thedisclosed catalyst systems using any suitable olefin polymerizationprocess using various types of polymerization reactors, polymerizationreactor systems, and polymerization reaction conditions. One such olefinpolymerization process for polymerizing olefins in the presence of acatalyst composition of the present invention can comprise contactingthe catalyst composition with an olefin monomer and optionally an olefincomonomer (one or more) in a polymerization reactor system underpolymerization conditions to produce an olefin polymer, wherein thecatalyst composition can comprise, as disclosed herein, an unbridgedmetallocene compound, an activator, and an optional co-catalyst. Thisinvention also encompasses any olefin polymers (e.g., ethylene polymers)produced by any of the polymerization processes disclosed herein.

As used herein, a “polymerization reactor” includes any polymerizationreactor capable of polymerizing (inclusive of oligomerizing) olefinmonomers and comonomers (one or more than one comonomer) to producehomopolymers, copolymers, terpolymers, and the like. The various typesof polymerization reactors include those that can be referred to as abatch reactor, slurry reactor, gas-phase reactor, solution reactor, highpressure reactor, tubular reactor, autoclave reactor, and the like, orcombinations thereof; or alternatively, the polymerization reactorsystem can comprise a slurry reactor, a gas-phase reactor, a solutionreactor, or a combination thereof. The polymerization conditions for thevarious reactor types are well known to those of skill in the art. Gasphase reactors can comprise fluidized bed reactors or staged horizontalreactors. Slurry reactors can comprise vertical or horizontal loops.High pressure reactors can comprise autoclave or tubular reactors.Reactor types can include batch or continuous processes. Continuousprocesses can use intermittent or continuous product discharge.Polymerization reactor systems and processes also can include partial orfull direct recycle of unreacted monomer, unreacted comonomer, and/ordiluent.

A polymerization reactor system can comprise a single reactor ormultiple reactors (2 reactors, more than 2 reactors, etc.) of the sameor different type. For instance, the polymerization reactor system cancomprise a slurry reactor, a gas-phase reactor, a solution reactor, or acombination of two or more of these reactors. Production of polymers inmultiple reactors can include several stages in at least two separatepolymerization reactors interconnected by a transfer device making itpossible to transfer the polymers resulting from the firstpolymerization reactor into the second reactor. The desiredpolymerization conditions in one of the reactors can be different fromthe operating conditions of the other reactor(s). Alternatively,polymerization in multiple reactors can include the manual transfer ofpolymer from one reactor to subsequent reactors for continuedpolymerization. Multiple reactor systems can include any combinationincluding, but not limited to, multiple loop reactors, multiple gasphase reactors, a combination of loop and gas phase reactors, multiplehigh pressure reactors, or a combination of high pressure with loopand/or gas phase reactors. The multiple reactors can be operated inseries, in parallel, or both. Accordingly, the present inventionencompasses polymerization reactor systems comprising a single reactor,comprising two reactors, and comprising more than two reactors. Thepolymerization reactor system can comprise a slurry reactor, a gas-phasereactor, or a solution reactor, in certain aspects of this invention, aswell as multi-reactor combinations thereof.

According to one aspect, the polymerization reactor system can compriseat least one loop slurry reactor comprising vertical or horizontalloops. Monomer, diluent, catalyst, and comonomer can be continuously fedto a loop reactor where polymerization occurs. Generally, continuousprocesses can comprise the continuous introduction of monomer/comonomer,a catalyst, and a diluent into a polymerization reactor and thecontinuous removal from this reactor of a suspension comprising polymerparticles and the diluent. Reactor effluent can be flashed to remove thesolid polymer from the liquids that comprise the diluent, monomer and/orcomonomer. Various technologies can be used for this separation stepincluding, but not limited to, flashing that can include any combinationof heat addition and pressure reduction, separation by cyclonic actionin either a cyclone or hydrocyclone, or separation by centrifugation.

A typical slurry polymerization process (also known as the particle formprocess) is disclosed, for example, in U.S. Pat. Nos. 3,248,179,4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191, 6,833,415, and8,822,608, each of which is incorporated herein by reference in itsentirety.

Suitable diluents used in slurry polymerization include, but are notlimited to, the monomer being polymerized and hydrocarbons that areliquids under reaction conditions. Examples of suitable diluentsinclude, but are not limited to, hydrocarbons such as propane,cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, andn-hexane. Some loop polymerization reactions can occur under bulkconditions where no diluent is used.

According to yet another aspect, the polymerization reactor system cancomprise at least one gas phase reactor (e.g., a fluidized bed reactor).Such reactor systems can employ a continuous recycle stream containingone or more monomers continuously cycled through a fluidized bed in thepresence of the catalyst under polymerization conditions. A recyclestream can be withdrawn from the fluidized bed and recycled back intothe reactor. Simultaneously, polymer product can be withdrawn from thereactor and new or fresh monomer can be added to replace the polymerizedmonomer. Such gas phase reactors can comprise a process for multi-stepgas-phase polymerization of olefins, in which olefins are polymerized inthe gaseous phase in at least two independent gas-phase polymerizationzones while feeding a catalyst-containing polymer formed in a firstpolymerization zone to a second polymerization zone. Representative gasphase reactors are disclosed in U.S. Pat. Nos. 5,352,749, 4,588,790,5,436,304, 7,531,606, and 7,598,327, each of which is incorporated byreference in its entirety herein.

According to still another aspect, the polymerization reactor system cancomprise a high pressure polymerization reactor, e.g., can comprise atubular reactor or an autoclave reactor. Tubular reactors can haveseveral zones where fresh monomer, initiators, or catalysts are added.Monomer can be entrained in an inert gaseous stream and introduced atone zone of the reactor. Initiators, catalysts, and/or catalystcomponents can be entrained in a gaseous stream and introduced atanother zone of the reactor. The gas streams can be intermixed forpolymerization. Heat and pressure can be employed appropriately toobtain optimal polymerization reaction conditions.

According to yet another aspect, the polymerization reactor system cancomprise a solution polymerization reactor wherein the monomer/comonomerare contacted with the catalyst composition by suitable stirring orother means. A carrier comprising an inert organic diluent or excessmonomer can be employed. If desired, the monomer/comonomer can bebrought in the vapor phase into contact with the catalytic reactionproduct, in the presence or absence of liquid material. Thepolymerization zone can be maintained at temperatures and pressures thatwill result in the formation of a solution of the polymer in a reactionmedium. Agitation can be employed to obtain better temperature controland to maintain uniform polymerization mixtures throughout thepolymerization zone. Adequate means are utilized for dissipating theexothermic heat of polymerization.

The polymerization reactor system can further comprise any combinationof at least one raw material feed system, at least one feed system forcatalyst or catalyst components, and/or at least one polymer recoverysystem. Suitable reactor systems can further comprise systems forfeedstock purification, catalyst storage and preparation, extrusion,reactor cooling, polymer recovery, fractionation, recycle, storage,loadout, laboratory analysis, and process control. Depending upon thedesired properties of the olefin polymer, hydrogen can be added to thepolymerization reactor as needed (e.g., continuously, pulsed, etc.).

Polymerization conditions that can be controlled for efficiency and toprovide desired polymer properties can include temperature, pressure,and the concentrations of various reactants. Polymerization temperaturecan affect catalyst productivity, polymer molecular weight, andmolecular weight distribution. Various polymerization conditions can beheld substantially constant, for example, for the production of aparticular grade of the olefin polymer (or ethylene polymer). A suitablepolymerization temperature can be any temperature below thede-polymerization temperature according to the Gibbs Free energyequation. Typically, this includes from about 60° C. to about 280° C.,for example, or from about 60° C. to about 120° C., depending upon thetype of polymerization reactor(s). In some reactor systems, thepolymerization temperature generally can be within a range from about70° C. to about 100° C., or from about 75° C. to about 95° C.

Suitable pressures will also vary according to the reactor andpolymerization type. The pressure for liquid phase polymerizations in aloop reactor is typically less than 1000 psig (6.9 MPa). Pressure forgas phase polymerization is usually at about 200 to 500 psig (1.4 MPa to3.4 MPa). High pressure polymerization in tubular or autoclave reactorsis generally run at about 20,000 to 75,000 psig (138 to 517 MPa).Polymerization reactors can also be operated in a supercritical regionoccurring at generally higher temperatures and pressures. Operationabove the critical point of a pressure/temperature diagram(supercritical phase) can offer advantages to the polymerizationreaction process.

Olefin monomers that can be employed with catalyst compositions andpolymerization processes of this invention typically can include olefincompounds having from 2 to 30 carbon atoms per molecule and having atleast one olefinic double bond, such as ethylene or propylene. In anaspect, the olefin monomer can comprise a C₂-C₂₀ olefin; alternatively,a C₂-C₂₀ alpha-olefin; alternatively, a C₂-C₁₀ olefin; alternatively, aC₂-C₁₀ alpha-olefin; alternatively, the olefin monomer can compriseethylene; or alternatively, the olefin monomer can comprise propylene(e.g., to produce a polypropylene homopolymer or a propylene-basedcopolymer).

When a copolymer (or alternatively, a terpolymer) is desired, the olefinmonomer and the olefin comonomer independently can comprise, forexample, a C₂-C₂₀ alpha-olefin. In some aspects, the olefin monomer cancomprise ethylene or propylene, which is copolymerized with at least onecomonomer (e.g., a C₂-C₂₀ alpha-olefin, a C₃-C₂₀ alpha-olefin, etc.).According to one aspect of this invention, the olefin monomer used inthe polymerization process can comprise ethylene. In this aspect, thecomonomer can comprise a C₃-C₁₀ alpha-olefin; alternatively, thecomonomer can comprise 1-butene, 1-pentene, 1-hexene, 1-octene,1-decene, styrene, or any combination thereof; alternatively, thecomonomer can comprise 1-butene, 1-hexene, 1-octene, or any combinationthereof; alternatively, the comonomer can comprise 1-butene;alternatively, the comonomer can comprise 1-hexene; or alternatively,the comonomer can comprise 1-octene.

EXAMPLES

The invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations to the scopeof this invention. Various other aspects, embodiments, modifications,and equivalents thereof which, after reading the description herein, maysuggest themselves to one of ordinary skill in the art without departingfrom the spirit of the present invention or the scope of the appendedclaims.

Melt index (MI, g/10 min) was determined in accordance with ASTM D1238at 190° C. with a 2,160 gram weight, and high load melt index (HLMI,g/10 min) was determined in accordance with ASTM D1238 at 190° C. with a21,600 gram weight. Density was determined in grams per cubic centimeter(g/cm³) on a compression molded sample, cooled at 15° C. per minute, andconditioned for 40 hours at room temperature in accordance with ASTMD1505 and ASTM D4703.

Molecular weights and molecular weight distributions were obtained usinga PL-GPC 220 (Polymer Labs, an Agilent Company) system equipped with aIR4 detector (Polymer Char, Spain) and three Styragel HMW-6E GPC columns(Waters, Mass.) running at 145° C. The flow rate of the mobile phase1,2,4-trichlorobenzene (TCB) containing 0.5 g/L2,6-di-t-butyl-4-methylphenol (BHT) was set at 1 mL/min, and polymersolution concentrations were in the range of 1.0-1.5 mg/mL, depending onthe molecular weight. Sample preparation was conducted at 150° C. fornominally 4 hr with occasional and gentle agitation, before thesolutions were transferred to sample vials for injection. An injectionvolume of about 200 μL was used. The integral calibration method wasused to deduce molecular weights and molecular weight distributionsusing a Chevron Phillips Chemical Company's HDPE polyethylene resin,MARLEX® BHB5003, as the standard. The integral table of the broadstandard was pre-determined in a separate experiment with SEC-MALS. Mnis the number-average molecular weight, Mw is the weight-averagemolecular weight, Mz is the z-average molecular weight, and Mp is thepeak molecular weight (location, in molecular weight, of the highestpoint of the molecular weight distribution curve). The IB parameter wasdetermined from the molecular weight distribution curve (plot ofdW/d(Log M) vs. Log M; normalized to an area equal to 1), and is definedas 1/[dW/d(Log M)]_(MAX).

Melt rheological characterizations were performed as follows.Small-strain (less than 10%) oscillatory shear measurements wereperformed on an Anton Paar MCR rheometer using parallel-plate geometry.All rheological tests were performed at 190° C. The complex viscosity|η*| versus frequency (ω) data were then curve fitted using the modifiedthree parameter Carreau-Yasuda (CY) empirical model to obtain thezero-shear viscosity—η₀, characteristic viscous relaxation time—τ_(η),and the breadth parameter—α (CY-a parameter). The simplifiedCarreau-Yasuda (CY) empirical model is as follows.

${{{\eta^{*}(\omega)}} = \frac{\eta_{0}}{\left\lbrack {1 + \left( {\tau_{\eta}\omega} \right)^{a}} \right\rbrack^{{({1 - n})}\text{/}a}}},$wherein: |η*(ω)|=magnitude of complex shear viscosity;

-   -   η₀=zero shear viscosity;    -   τ_(η)=viscous relaxation time (Tau(η));    -   a=“breadth” parameter (CY-a parameter);    -   n=fixes the final power law slope, fixed at 2/11; and    -   ω=angular frequency of oscillatory shearing deformation.

Details of the significance and interpretation of the CY model andderived parameters may be found in: C. A. Hieber and H. H. Chiang,Rheol. Acta, 28, 321 (1989); C. A. Hieber and H. H. Chiang, Polym. Eng.Sci., 32, 931 (1992); and R. B. Bird, R. C. Armstrong and O. Hasseger,Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics, 2nd Edition,John Wiley & Sons (1987); each of which is incorporated herein byreference in its entirety.

The ATREF procedure was as follows. Forty mg of the polymer sample and20 mL of 1,2,4-trichlorobenzene (TCB) were sequentially charged into avessel on a PolyChar TREF 200+instrument. After dissolving the polymer,an aliquot (500 microliters) of the polymer solution was loaded on thecolumn (stainless steel shots) at 150° C. and cooled at 0.5° C./min to25° C. Then, the elution was begun with a 0.5 mL/min TCB flow rate andheating at 1° C./min up to 120° C., and analyzing with an IR detector.The peak ATREF temperature is the location, in temperature, of thehighest point of the ATREF curve.

Dart impact strength (g/mil) can be measured in accordance with ASTMD1709 (method A). Machine direction (MD) and transverse direction (TD)Elmendorf tear strengths (g/mil) were measured on a Testing MachinesInc. tear tester (Model 83-11-00) in accordance with ASTM D1922. Filmhaze (%) was determined in accordance with ASTM D1003, and film clarity(%) was determined in accordance with ASTM 105.

Metals content, such as the amount of catalyst residue in the ethylenepolymer or film, can be determined by ICP analysis on a PerkinElmerOptima 8300 instrument. Polymer samples can be ashed in a Thermolynefurnace with sulfuric acid overnight, followed by acid digestion in aHotBlock with HCl and HNO₃ (3:1 v:v).

Fluorided silica-coated alumina activator-supports (FSCA) were preparedas follows. Bohemite was obtained from W.R. Grace & Company under thedesignation “Alumina A” and having a surface area of 300 m²/g, a porevolume of 1.3 mL/g, and an average particle size of 100 microns. Thealumina was first calcined in dry air at about 600° C. for approximately6 hours, cooled to ambient temperature, and then contacted withtetraethylorthosilicate in isopropanol to equal 25 wt. % SiO₂. Afterdrying, the silica-coated alumina was calcined at 600° C. for 3 hours.Fluorided silica-coated alumina (7 wt. % F) was prepared by impregnatingthe calcined silica-coated alumina with an ammonium bifluoride solutionin methanol, drying, and then calcining for 3 hours at 600° C. in dryair. Afterward, the fluorided silica-coated alumina (FSCA) was collectedand stored under dry nitrogen, and was used without exposure to theatmosphere.

Examples 1-4 were produced using the following polymerization procedure.The polymerization runs were conducted in a one-gallon (3.8-L) stainlesssteel reactor, and isobutane (2 L) was used in all runs. Under anisobutane purge, the organoaluminum compound (0.8 mL of 1M TIBA inheptanes), the activator-support (FSCA, 115 mg), and the metallocenecompound (bis(n-butyl cyclopentadienyl) zirconium dichloride, 2 mg) wereadded in that order through a charge port while slowly venting isobutanevapor. The charge port was closed and isobutane was added. The contentsof the reactor were stirred and heated to the desired run temperature ofabout 75° C., and ethylene and 1-hexene (60 to 140 g) were thenintroduced into the reactor (no hydrogen was used). Ethylene was fed ondemand to maintain the target pressure of 260 psig pressure for the 30minute length of the polymerization run. The reactor was maintained atthe desired temperature throughout the run by an automatedheating-cooling system. After venting of the reactor, purging, andcooling, the resulting polymer product was dried under reduced pressure.

Cast film samples at a 2-mil thickness (50 microns) were produced fromExamples 1-7 on a laboratory-scale cast film line using typical linearlow density polyethylene conditions (LLDPE) as follows: 152 mm diewidth, 0.508 mm die gap, 16 mm diameter single-screw extruder(L/D=24-27), 0.5 kg/hr output rate, and 204° C. barrel and die settemperatures. Cooling was accomplished with chill roll at about 23° C.These particular processing conditions were chosen because the cast filmproperties so obtained are typically representative of those obtainedfrom larger, commercial scale film casting conditions.

Examples 1-8

Examples 1-4 were produced as described above. Comparative Examples 5-7were commercially-available LLDPE (ethylene copolymer) resins fromChevron-Phillips Chemical Company LP, while Comparative Example 8 was acommercially-available LLDPE (ethylene copolymer) resin from The DowChemical Company.

Table I summarizes various melt flow, rheology, molecular weight, anddensity properties of Examples 1-8. FIGS. 1-8 illustrate the ATREFprofiles of the polymers of Examples 1-8, respectively, and certaininformation from the ATREF profiles is summarized in Table II. FIG. 9illustrates the molecular weight distribution (amount of polymer versusthe logarithm of molecular weight) for the polymer of Example 1. TableIII summarizes tear resistance and optical properties of the cast filmsof Examples 1-7. Generally, the polymers of Examples 1-4 had densitiesin the 0.91-0.925 g/cm³ range, melt index values in the 1.5-2.5 g/10 minrange, ratios of Mw/Mn in the 2.5-4 range, ratios of Mz/Mw in the 1.8-2range, and CY-a parameters in the 0.5-0.6 range. ATREF profiles ofExamples 1-4 had single peaks at peak ATREF temperatures in the 80-90°C. range, with less than 12 wt. % of the polymer eluting above 91° C.,and substantially none of the polymer eluting above 100° C.

Unexpectedly, Examples 1-4 had a single ATREF peak (between 40-110° C.),whereas Examples 6-8 had multiple peaks on the respective ATREFprofiles. Example 5 had a single ATREF peak, however Example 5 had amuch higher CY-a parameter and excessive film haze (˜15%). As shown inTable III, the ethylene copolymers of inventive Examples 1-4 had thebeneficial and surprising combination of excellent MD tear strength(greater than 300 g/mil) and low film haze (less than 11%, and oftenless than 6%). The comparative examples could provide either acceptableMD tear strength or acceptable film haze, but not both.

While not wishing to be bound by the following theory, it is believedthat the combined polymer properties of density, molecular weight (e.g.,narrow Mw/Mn and Mz/Mw), rheology (e.g., CY-a and relaxation time), andATREF (e.g., a single peak and small amounts eluting at elevatedtemperatures) result in the beneficial and surprising combination offilm properties: excellent MD tear strength (greater than 300 g/mil) andlow haze (less than 11%, and often less than 6%).

TABLE I Examples 1-8. MI HLMI Density Example (g/10 min) (g/10 min)HLMI/MI (g/cc) 1 2.0 38 18.5 0.916 2 1.7 31 17.6 0.914 3 2.0 35 17.70.920 4 2.1 39 18.2 0.923 5 2.0 30 15.2 0.920 6 1.3 22 16.8 0.918 7 0.813 16.0 0.917 8 1.0 — — 0.916 Mn/1000 Mw/1000 Mz/1000 Mp/1000 τ_(η)Example (g/mol) (g/mol) (g/mol) (g/mol) Mw/Mn Mz/Mw IB (sec) CY-a 1 39.3103 194 84 2.6 1.88 0.96 6.57E−03 0.54 2 32.6 108 208 93 3.3 1.94 1.018.14E−03 0.56 3 30.9 109 214 89 3.5 1.97 0.99 7.24E−03 0.55 4 29.0 107210 87 3.7 1.96 1.02 7.11E−03 0.55 5 44.5 108 192 93 2.4 1.78 0.957.66E−03 0.69 6 54.3 119 200 103 2.2 1.68 0.89 1.06E−02 0.62 7 46.7 165298 143 3.5 1.81 0.95 1.51E−02 0.56 8 46.8 127 250 96 2.7 1.98 1.142.78E−02 0.42

TABLE II Examples 1-8 - ATREF Properties. <40° C. 40-76° C. 76-86°C. >86° C. >91° C. >100° C. Example (wt. %) (wt. %) (wt. %) (wt. %) (wt.%) (wt. %) 1 1 41 44 14 1.9 0 2 2 39 49 10 1.5 0 3 1 25 48 25 2.5 0 4 216 39 43 10 0 5 — — — — — — 6 1 36 42 21 — — 7 — — — — — — 8 1 49 17 33— — 1^(st) Peak Temp. 2^(nd) Peak Temp. 3^(rd) Peak Temp. Example (° C.)(° C.) (° C.) 1 80.2 — — 2 80.3 — — 3 85.0 — — 4 88.5 — — 5 — — — 6 7689 — 7 — — — 8 69 84 96

TABLE III Examples 1-7 — Film Properties. Tear MD Tear TD Tear RatioHaze Clarity Example (g/mil) (g/mil) MD/TD (%) (%) 1 318 605 0.52  5.281.8 2 307 369 0.83  3.0 82.1 3 303 484 0.63  5.5 84.2 4 323 539 0.6010.7 83.4 5 313 503 0.62 15.1 81.5 6 209 445 0.47  4.8 83.6 7 145 4800.30  5.4 85.1

The invention is described above with reference to numerous aspects andspecific examples. Many variations will suggest themselves to thoseskilled in the art in light of the above detailed description. All suchobvious variations are within the full intended scope of the appendedclaims. Other aspects of the invention can include, but are not limitedto, the following (aspects are described as “comprising” but,alternatively, can “consist essentially of” or “consist of”):

Aspect 1. An ethylene polymer characterized by a density in a range fromabout 0.908 to about 0.925 g/cm³, a melt index in a range from about 0.5to about 3 g/10 min, a ratio of Mw/Mn in a range from about 2 to about4, a ratio of Mz/Mw in a range from about 1.6 to about 2.3, a CY-aparameter in a range from about 0.45 to about 0.6, and an ATREF profilecharacterized by a single peak (between 40-110° C.) at a peak ATREFtemperature in a range from about 76 to about 88° C., and by less thanor equal to about 4.5 wt. % of the polymer eluting above a temperatureof 91° C.

Aspect 2. The polymer defined in aspect 1, wherein less than or equal toabout 4 wt. %, less than or equal to about 3.5 wt. %, less than or equalto about 3 wt. % of the polymer, etc., elutes above a temperature of 91°C.

Aspect 3. An ethylene polymer characterized by a density in a range fromabout 0.908 to about 0.925 g/cm³, a melt index in a range from about 0.5to about 3 g/10 min, a ratio of Mw/Mn in a range from about 2 to about4, a ratio of Mz/Mw in a range from about 1.6 to about 2.3, a CY-aparameter in a range from about 0.45 to about 0.6, and an ATREF profilecharacterized by a single peak (between 40-110° C.) at a peak ATREFtemperature in a range from about 76 to about 90° C., by less than orequal to about 12 wt. % of the polymer eluting above a temperature of91° C., and by less than or equal to about 0.1 wt. % of the polymereluting above a temperature of 100° C.

Aspect 4. The polymer defined in aspect 3, wherein less than or equal toabout 11 wt. %, less than or equal to about 10 wt. %, less than or equalto about 4.5 wt. %, less than or equal to about 3.5 wt. %, etc., elutesabove a temperature of 91° C.

Aspect 5. The polymer defined in any one of the preceding aspects,wherein less than or equal to about 0.1 wt. %, less than or equal toabout 0.09 wt. %, less than or equal to about 0.07 wt. %, less than orequal to about 0.05 wt. %, etc., elutes above a temperature of 100° C.

Aspect 6. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a melt index (MI) in any rangedisclosed herein, e.g., from about 0.5 to about 2.5 g/10 min, from about1 to about 2.5 g/10 min, from about 0.5 to about 2.2 g/10 min, fromabout 0.8 to about 2.2 g/10 min, etc.

Aspect 7. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a high load melt index (HLMI) in anyrange disclosed herein, e.g., from about 10 to about 50 g/10 min, fromabout 12 to about 40 g/10 min, from about 18 to about 45 g/10 min, fromabout 15 to about 40 g/10 min, etc.

Aspect 8. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a ratio of HLMI/MI in any rangedisclosed herein, e.g., from about 10 to about 30, from about 15 toabout 30, from about 10 to about 25, from about 15 to about 25, etc.

Aspect 9. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a density in any range disclosedherein, e.g., from about 0.908 to about 0.922 g/cm³, from about 0.908 toabout 0.92 g/cm³, from about 0.91 to about 0.925 g/cm³, from about 0.91to about 0.922 g/cm³, from about 0.91 to about 0.92 g/cm³, etc.

Aspect 10. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a ratio of Mw/Mn in any range disclosedherein, e.g., from about 2.2 to about 4, from about 2.4 to about 4, fromabout 2 to about 3.8, from about 2.2 to about 3.8, from about 2.4 toabout 3.8, from about 2 to about 3.6, from about 2.3 to about 3.6, etc.

Aspect 11. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a ratio of Mz/Mw in any range disclosedherein, e.g., from about 1.7 to about 2.3, from about 1.8 to about 2.3,from about 1.6 to about 2.2, from about 1.7 to about 2.2, from about 1.7to about 2.1, from about 1.8 to about 2.2, from about 1.8 to about 2.1,etc.

Aspect 12. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a Mn in any range disclosed herein,e.g., from about 20,000 to about 60,000 g/mol, from about 20,000 toabout 55,000 g/mol, from about 20,000 to about 50,000 g/mol, from about25,000 to about 60,000 g/mol, from about 25,000 to about 55,000 g/mol,from about 25,000 to about 50,000 g/mol, from about 25,000 to about45,000 g/mol, etc.

Aspect 13. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a Mw in any range disclosed herein,e.g., from about 80,000 to about 180,000 g/mol, from about 80,000 toabout 160,000 g/mol, from about 95,000 to about 175,000 g/mol, fromabout 95,000 to about 140,000 g/mol, etc.

Aspect 14. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a Mp in any range disclosed herein,e.g., from about 60,000 to about 130,000 g/mol, from about 70,000 toabout 130,000 g/mol, from about 60,000 to about 115,000 g/mol, fromabout 70,000 to about 115,000 g/mol, from about 75,000 to about 95,000g/mol, etc.

Aspect 15. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a Mz in any range disclosed herein,e.g., from about 150,000 to about 300,000 g/mol, from about 175,000 toabout 275,000 g/mol, from about 175,000 to about 250,000 g/mol, fromabout 185,000 to about 265,000 g/mol, from about 185,000 to about235,000 g/mol, etc.

Aspect 16. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has an IB parameter in any range disclosedherein, e.g., from about 0.9 to about 1.05, from about 0.92 to about1.05, from about 0.93 to about 1.03, from about 0.95 to about 1.03, etc.

Aspect 17. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a CY-a parameter in any range disclosedherein, e.g., from about 0.45 to about 0.58, from about 0.48 to about0.6, from about 0.48 to about 0.58, from about 0.5 to about 0.6, fromabout 0.52 to about 0.59, etc.

Aspect 18. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a τ_(η) (relaxation time) in any rangedisclosed herein, e.g., from about 4×10⁻³ sec to about 2×10⁻² sec, fromabout 5×10⁻³ sec to about 1×10⁻² sec, from about 5×10⁻³ sec to about9×10⁻³ sec, etc.

Aspect 19. The polymer defined in any one of the preceding aspects,wherein the peak ATREF temperature is in a range from about 77 to about89° C., from about 76 to about 88° C., from about 78 to about 87° C.,from about 79 to about 86° C., etc.

Aspect 20. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has an ATREF profile characterized by fromabout 0.05 to about 5 wt. % (or from about 0.1 to about 3 wt. %, or fromabout 0.3 to about 2 wt. %) of the polymer eluting below a temperatureof 40° C., by from about 14 to about 45 wt. % (or from about 16 to about44 wt. %, or from about 22 to about 42 wt. %) of the polymer elutingbetween 40 and 76° C., by from about 35 to about 53 wt. % (or from about38 to about 52 wt. %, or from about 40 to about 51 wt. %) of the polymereluting between 76 and 86° C., and the remainder of the polymer (toreach 100 wt. %) eluting above a temperature of 86° C.

Aspect 21. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer has a unimodal molecular weightdistribution (single peak).

Aspect 22. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer is a single reactor product, e.g., not apost-reactor blend of two polymers, for instance, having differentmolecular weight characteristics.

Aspect 23. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer comprises an ethylene/α-olefin copolymer.

Aspect 24. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer comprises an ethylene/1-butene copolymer,an ethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.

Aspect 25. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer comprises an ethylene/1-hexene copolymer.

Aspect 26. The polymer defined in any one of the preceding aspects,wherein the ethylene polymer contains, independently, less than 0.1 ppm(by weight), less than 0.08 ppm, less than 0.05 ppm, less than 0.03 ppm,etc., of hafnium and titanium.

Aspect 27. The polymer defined in any one of the preceding aspects,wherein the polymer further comprises any additive disclosed herein,e.g., an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a filler, a polymer processing aid, a UV additive,etc., or combinations thereof.

Aspect 28. An article of manufacture comprising (or produced from) theethylene polymer defined in any one of aspects 1-27.

Aspect 29. An article of manufacture comprising (or produced from) theethylene polymer defined in any one of aspects 1-27, wherein the articleis an agricultural film, an automobile part, a bottle, a container forchemicals, a drum, a fiber or fabric, a food packaging film orcontainer, a food service article, a fuel tank, a geomembrane, ahousehold container, a liner, a molded product, a medical device ormaterial, an outdoor storage product, outdoor play equipment, a pipe, asheet or tape, a toy, or a traffic barrier.

Aspect 30. A film comprising (or produced from) the ethylene polymerdefined in any one of aspects 1-27.

Aspect 31. The film defined in aspect 30, wherein the film has a haze(with or without additives) in any range disclosed herein, e.g., lessthan or equal to about 10%, less than or equal to about 8%, from about 2to about 10%, from about 2 to about 8%, from about 2 to about 7%, etc.

Aspect 32. The film defined in aspect 30 or 31, wherein the film has aMD Elmendorf tear strength in any range disclosed herein, e.g., fromabout 200 to about 500 g/mil, from about 250 to about 500 g/mil, fromabout 300 to about 500 g/mil, from about 250 to about 400 g/mil, fromabout 275 to about 350 g/mil, etc.

Aspect 33. The film defined in any one of aspects 30-32, wherein thefilm has a TD Elmendorf tear strength in any range disclosed herein,e.g., from about 300 to about 800 g/mil, from about 300 to about 700g/mil, from about 300 to about 625 g/mil, from about 350 to about 650g/mil, etc.

Aspect 34. The film defined in any one of aspects 30-33, wherein thefilm has a clarity (with or without additives) in any range disclosedherein, e.g., at least about 70%, at least about 75%, at least about80%, etc.

Aspect 35. The film defined in any one of aspects 30-34, wherein thefilm has an average thickness in any range disclosed herein, e.g., fromabout 0.5 to about 20 mils, from about 0.5 to about 8 mils, from about0.8 to about 5 mils, from about 0.7 to about 2 mils, etc.

Aspect 36. The film defined in any one of aspects 30-35, wherein thefilm has a dart impact strength in any range disclosed herein, e.g.,greater than or equal to about 300 g/mil, greater than or equal to about500 g/mil, greater than or equal to about 1000 g/mil, greater than orequal to about 1400 g/mil, etc.

Aspect 37. The film defined in any one of aspects 30-36, wherein thefilm has a ratio of MD Elmendorf tear strength to TD Elmendorf tearstrength (MD:TD) in any range disclosed herein, e.g., from about 0.3:1to about 0.9:1, from about 0.4:1 to about 0.9:1, from about 0.5:1 toabout 0.9:1, from about 0.5:1 to about 0.85:1, etc.

Aspect 38. The film defined in any one of aspects 30-37, wherein thefilm is a blown film.

Aspect 39. The film defined in any one of aspects 30-37, wherein thefilm is a cast film.

Aspect 40. A catalyst composition comprising any unbridged metallocenecompound disclosed herein, any activator disclosed herein, andoptionally, any co-catalyst disclosed herein.

Aspect 41. The composition defined in aspect 40, wherein the unbridgedmetallocene compound comprises an unbridged zirconium or hafnium basedmetallocene compound containing two cyclopentadienyl groups, two indenylgroups, or a cyclopentadienyl and an indenyl group.

Aspect 42. The composition defined in aspect 40, wherein the unbridgedmetallocene compound comprises an unbridged zirconium based metallocenecompound containing two cyclopentadienyl groups.

Aspect 43. The composition defined in aspect 40, wherein the unbridgedmetallocene compound comprises an unbridged zirconium based metallocenecompound containing two indenyl groups.

Aspect 44. The composition defined in any one of aspects 41-43, whereinone (or both) of the cyclopentadienyl and/or indenyl groups isalkyl-substituted.

Aspect 45. The composition defined in any one of aspects 40-44, whereinthe activator comprises an activator-support, an aluminoxane compound,an organoboron or organoborate compound, an ionizing ionic compound, orany combination thereof.

Aspect 46. The composition defined in any one of aspects 40-44, whereinthe activator comprises an aluminoxane compound.

Aspect 47. The composition defined in any one of aspects 40-44, whereinthe activator comprises an organoboron or organoborate compound.

Aspect 48. The composition defined in any one of aspects 40-44, whereinthe activator comprises an ionizing ionic compound.

Aspect 49. The composition defined in any one of aspects 40-44, whereinthe activator comprises an activator-support, the activator-supportcomprising any solid oxide treated with any electron-withdrawing aniondisclosed herein.

Aspect 50. The composition defined in any one of aspects 40-44, whereinthe activator comprises fluorided alumina, chlorided alumina, bromidedalumina, sulfated alumina, fluorided silica-alumina, chloridedsilica-alumina, bromided silica-alumina, sulfated silica-alumina,fluorided silica-zirconia, chlorided silica-zirconia, bromidedsilica-zirconia, sulfated silica-zirconia, fluorided silica-titania,fluorided-chlorided silica-coated alumina, fluorided silica-coatedalumina, sulfated silica-coated alumina, phosphated silica-coatedalumina, or any combination thereof.

Aspect 51. The composition defined in any one of aspects 40-44, whereinthe activator comprises a fluorided solid oxide and/or a sulfated solidoxide.

Aspect 52. The composition defined in any one of aspects 40-51, whereinthe catalyst composition comprises a co-catalyst, e.g., any co-catalystdisclosed herein.

Aspect 53. The composition defined in any one of aspects 40-52, whereinthe co-catalyst comprises any organoaluminum compound disclosed herein.

Aspect 54. The composition defined in aspect 53, wherein theorganoaluminum compound comprises trimethylaluminum, triethylaluminum,triisobutylaluminum, or a combination thereof.

Aspect 55. The composition defined in any one of aspects 49-54, whereinthe catalyst composition comprises an unbridged metallocene compound, asolid oxide treated with an electron-withdrawing anion, and anorganoaluminum compound.

Aspect 56. The composition defined in any one of aspects 49-55, whereinthe catalyst composition is substantially free of aluminoxane compounds,organoboron or organoborate compounds, ionizing ionic compounds, orcombinations thereof.

Aspect 57. The composition defined in any one of aspects 40-56, whereinthe catalyst composition is produced by a process comprising contacting,the unbridged metallocene compound, the activator, and the co-catalyst.

Aspect 58. An olefin polymerization process, the process comprisingcontacting the catalyst composition defined in any one of aspects 40-57with an olefin monomer and an optional olefin comonomer in apolymerization reactor system under polymerization conditions to producean olefin polymer.

Aspect 59. The process defined in aspect 58, wherein the olefin monomercomprises any olefin monomer disclosed herein, e.g., any C₂-C₂₀ olefin.

Aspect 60. The process defined in aspect 58 or 59, wherein the olefinmonomer and the optional olefin comonomer independently comprise aC₂-C₂₀ alpha-olefin.

Aspect 61. The process defined in any one of aspects 58-60, wherein theolefin monomer comprises ethylene.

Aspect 62. The process defined in any one of aspects 58-61, wherein thecatalyst composition is contacted with ethylene and an olefin comonomercomprising a C₃-C₁₀ alpha-olefin.

Aspect 63. The process defined in any one of aspects 58-62, wherein thecatalyst composition is contacted with ethylene and an olefin comonomercomprising 1-butene, 1-hexene, 1-octene, or a mixture thereof.

Aspect 64. The process defined in any one of aspects 58-63, wherein thepolymerization reactor system comprises a batch reactor, a slurryreactor, a gas-phase reactor, a solution reactor, a high pressurereactor, a tubular reactor, an autoclave reactor, or a combinationthereof.

Aspect 65. The process defined in any one of aspects 58-64, wherein thepolymerization reactor system comprises a slurry reactor, a gas-phasereactor, a solution reactor, or a combination thereof.

Aspect 66. The process defined in any one of aspects 58-65, wherein thepolymerization reactor system comprises a loop slurry reactor.

Aspect 67. The process defined in any one of aspects 58-66, wherein thepolymerization reactor system comprises a single reactor.

Aspect 68. The process defined in any one of aspects 58-66, wherein thepolymerization reactor system comprises 2 reactors.

Aspect 69. The process defined in any one of aspects 58-66, wherein thepolymerization reactor system comprises more than 2 reactors.

Aspect 70. The process defined in any one of aspects 58-69, wherein theolefin polymer comprises any olefin polymer disclosed herein.

Aspect 71. The process defined in any one of aspects 58-70, wherein theolefin polymer comprises an ethylene/1-butene copolymer, anethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.

Aspect 72. The process defined in any one of aspects 58-71, wherein theolefin polymer comprises an ethylene/1-hexene copolymer.

Aspect 73. The process defined in any one of aspects 58-72, wherein thepolymerization conditions comprise a polymerization reaction temperaturein a range from about 60° C. to about 120° C. and a reaction pressure ina range from about 200 to about 1000 psig (about 1.4 to about 6.9 MPa).

Aspect 74. The process defined in any one of aspects 58-73, wherein thepolymerization conditions are substantially constant, e.g., for aparticular polymer grade.

Aspect 75. The process defined in any one of aspects 58-74, wherein nohydrogen is added to the polymerization reactor system.

Aspect 76. The process defined in any one of aspects 58-74, whereinhydrogen is added to the polymerization reactor system.

Aspect 77. The process defined in any one of aspects 58-76, wherein theolefin polymer produced is defined in any one of aspects 1-27.

Aspect 78. An olefin polymer produced by the olefin polymerizationprocess defined in any one of aspects 58-76.

Aspect 79. An ethylene polymer defined in any one of aspects 1-27produced by the process defined in any one of aspects 58-76.

Aspect 80. An article (e.g., a blown film or a cast film) comprising thepolymer defined in any one of aspects 78-79.

We claim:
 1. A film comprising an ethylene polymer, wherein the filmhas: a haze in a range from about 2 to about 10%; and a MD Elmendorftear strength in a range from about 200 to about 500 g/mil; and whereinthe ethylene polymer has: a density in a range from about 0.908 to about0.925 g/cm³; a melt index in a range from about 0.5 to about 3 g/10 min;a ratio of Mw/Mn in a range from about 2 to about 4; a ratio of Mz/Mw ina range from about 1.6 to about 2.3; a CY-a parameter in a range fromabout 0.45 to about 0.6; and an ATREF profile characterized by a singlepeak at a peak ATREF temperature in a range from about 76 to about 88°C., and by less than or equal to about 4.5 wt % of the polymer elutingabove a temperature of 91° C.
 2. The film of claim 1, wherein: the peakATREF temperature is in a range from about 79 to about 86° C.; and lessthan or equal to about 3.5 wt % of the polymer elutes above atemperature of 91° C.
 3. The film of claim 1, wherein: the haze is in arange from about 2 to about 8%; and the MD Elmendorf tear strength is ina range from about 250 to about 400 g/mil.
 4. The film of claim 1,wherein: the ethylene polymer has a unimodal molecular weightdistribution; and the ethylene polymer comprises an ethylene/1-butenecopolymer, an ethylene/1-hexene copolymer, an ethylene/1-octenecopolymer, or a combination thereof.
 5. The film of claim 4, wherein thefilm is a blown film having an average thickness in a range from about0.8 to about 5 mils.
 6. The film of claim 4, wherein: the density is ina range from about 0.91 to about 0.922 g/cm³; the melt index is in arange from about 1 to about 2.5 g/10 min; the ratio of Mw/Mn is in arange from about 2.2 to about 3.8; the ratio of Mz/Mw is in a range fromabout 1.7 to about 2.2; and the CY-a parameter is in a range from about0.5 to about 0.6.
 7. The film of claim 6, wherein the film is a castfilm having an average thickness in a range from about 0.5 to about 8mils.
 8. The film of claim 4, wherein the film has: a ratio of MDElmendorf tear strength to TD Elmendorf tear strength (MD:TD) in a rangefrom about 0.5:1 to about 0.9:1; and a dart impact strength of greaterthan or equal to about 500 g/mil.
 9. The film of claim 1, wherein theethylene polymer has: a Mn in a range from about 25,000 to about 55,000g/mol; and a high load melt index (HLMI) in a range from about 18 toabout 45 g/10 min.
 10. The film of claim 1, wherein the ethylene polymerhas: a Mz in a range from about 175,000 to about 275,000 g/mol; and anIB parameter in a range from about 0.9 to about 1.05.
 11. The film ofclaim 1, wherein: the haze is in a range from about 2 to about 7%; andthe MD Elmendorf tear strength is in a range from about 300 to about 400g/mil.
 12. An ethylene polymer having: a density in a range from about0.908 to about 0.925 g/cm³; a melt index in a range from about 0.5 toabout 3 g/10 min; a ratio of Mw/Mn in a range from about 2 to about 4; aratio of Mz/Mw in a range from about 1.6 to about 2.3; a CY-a parameterin a range from about 0.45 to about 0.6; and an ATREF profilecharacterized by a single peak at a peak ATREF temperature in a rangefrom about 76 to about 88° C., and by less than or equal to about 4.5 wt% of the polymer eluting above a temperature of 91° C.
 13. The polymerof claim 12, wherein the ethylene polymer has: a Mw in a range fromabout 80,000 to about 180,000 g/mol; and a relaxation time (τ_(η)) in arange from about 4×10⁻³ sec to about 2×10⁻² sec.
 14. An article ofmanufacture comprising the ethylene polymer of claim
 13. 15. The polymerof claim 12, wherein: the density is in a range from about 0.91 to about0.922 g/cm³; the melt index is in a range from about 1 to about 2.5 g/10min; the ratio of Mw/Mn is in a range from about 2.2 to about 3.8; theratio of Mz/Mw is in a range from about 1.7 to about 2.2; the CY-aparameter is in a range from about 0.52 to about 0.59; the peak ATREFtemperature is in a range from about 79 to about 86° C.; and less thanor equal to about 3.5 wt % of the polymer elutes above a temperature of91° C.
 16. The polymer of claim 12, wherein the ATREF profile is furthercharacterized by from about 0.05 to about 5 wt % of the polymer elutingbelow a temperature of 40° C., from about 14 to about 45 wt % of thepolymer eluting between 40 and 76° C., from about 35 to about 53 wt % ofthe polymer eluting between 76 and 86° C., and the remainder of thepolymer eluting above a temperature of 86° C.
 17. An ethylene polymerhaving: a density in a range from about 0.908 to about 0.925 g/cm³; amelt index in a range from about 0.5 to about 3 g/10 min; a ratio ofMw/Mn in a range from about 2 to about 4; a ratio of Mz/Mw in a rangefrom about 1.6 to about 2.3; a CY-a parameter in a range from about 0.45to about 0.6; and an ATREF profile characterized by a single peak at apeak ATREF temperature in a range from about 76 to about 90° C., by lessthan or equal to about 12 wt % of the polymer eluting above atemperature of 91° C., and by less than or equal to about 0.1 wt % ofthe polymer eluting above a temperature of 100° C.
 18. An article ofmanufacture comprising the ethylene polymer of claim
 17. 19. The polymerof claim 17, wherein: the peak ATREF temperature is in a range fromabout 77 to about 89° C.; less than or equal to about 11 wt % of thepolymer elutes above a temperature of 91° C.; and less than or equal toabout 0.07 wt % of the polymer elutes above a temperature of 100° C. 20.The polymer of claim 17, wherein the ethylene polymer: has a unimodalmolecular weight distribution; and contains less than 0.1 ppm,independently, of hafnium and titanium.
 21. The polymer of claim 17,wherein: the ethylene polymer further comprises an additive selectedfrom an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a filler, a polymer processing aid, a UV additive,or a combination thereof; and the ethylene polymer comprises anethylene/1-butene copolymer, an ethylene/1-hexene copolymer, anethylene/1-octene copolymer, or a combination thereof.